This invention relates to improvements in the field of orthodontics It presents a new solution to a problem which has arisen with some modern archwires because they cannot easily be bent at their ends to prevent them from slipping excessively lengthwise, i.e. in the mesial-distal direction.
According to conventional orthodontic practice, a plurality of wire-receiving brackets are banded or bonded to the teeth, except that the distal molars are provided with tubes. A parabolic archwire has its opposite ends inserted in the molar tubes, and the archwire is inserted into wire-receiving slots of the brackets on the teeth. Ligature wires are used to tie the wire to the brackets. When attached to the brackets, the wire is under flexural and/or torsional stresses which, due to the resiliency of the vire, exert corrective tooth-moving forces on the teeth.
Until the advent of ultraelastic wires such as those formed of shape memory alloys as disclosed in my earlier U.S. Pat. No. 4,037,324, it was customary orthodontic practice to form bends in the distal ends of stainless steel archwires immediately at the distal ends of the molar tubes. However, when using wires formed of shape memory alloys, such as those disclosed in U.S. Pats. 4,037,324 and 4,490,112, the physical properties of the wires resist the formation of an effective distal bend. Without a distal bend, a wire is free to slide lengthwise, i.e. in a mesial-distal direction, until one end protrudes excessively from a molar tube so it contacts, irritates, and produces ulcerations in the patient's mouth. This problem can be accentuated when the coefficient of friction between the wire and the brackets is relatively low, and when there are no bends or auxiliaries formed in or attached to the archwire. Although v-shaped bends have been formed in archwires for the attachment of hooks and other devices, no manufacturer or supplier has provided archwires which are prevent to reduce the extent of sliding movement of the wires relative to the brackets and molar tubes.
Conventional brackets to which the invention is applicable have slots with measurements of 0.018 to 0.022 inch in the gingival-occlusal direction, when used with wires of square, round or rectangular cross section measuring, 0.014 to 0.0215 inch in the gingival-occlusal direction. Presently available small edgewise brackets have wire-receiving slots which measure 018 inch and, 0.025 inch ,respectively, in the gingival-occlusal and buccal-lingual directions. The corresponding measurements of the slots in heavy edgewise brackets measure 0.022 and 0.028 inch. Small and large edgewise brackets are used with round wires with diameters of 0.014, 0.016 and 0.018 inch; square wires measuring 0.016, 0.017 and 0.018 inch; and, rectangular wires measuring 0.016 .times.0.022 inch, 0.016 .times.0.025 inch, 0.017 .times.0.022 inch, 0.017 .times.0.025 inch, 0.018 .times.0.022 inch, and 0.018 .times.0.025 inch. Additionally, large edgewise brackets are used with 0.020 inch and 0.022 inch round wires, 0.020 inch square wires, and rectangular wires which are 0.019 .times.0.026 inch, 0.021 .times.0.022 inch, 0.021 .times.0.025 inch, and 0.0215 .times.0.028 inch.